In both commercial and residential construction, electrical conductors which run between various locations are typically housed in an outer protective jacket. Such structures are referred to as electrical conduits. One such conduit is a flexible, metallic conduit where the conduit includes an outer helically convoluted metal jacket for enhanced flexibility. Another such conduit is a rigid extruded metal tubing commonly referred to as EMT. The conduit is terminated to an electrical junction or outlet box and the individual conductors are terminated to an electrical device supported in the junction box.
In order to suitably retain the conduit in the junction box, a conduit connector or fitting is employed to terminate the conduit and to mechanically and electrically secure the conduit to the junction box itself. Conduit connectors of this type are well-known in the electrical connection art. These connectors typically include a cylindrical body which supports therein an end extent of the conduit. The cylindrical body is attachable to the junction box through a knockout opening to allow passage of the conductors into the junction box. A screw may be interposed through the wall of the connector body to engage the conduit thereby securely retaining the conduit within such connector body.
As mentioned, the connector is mechanically secured to the junction box. One end of the connector is positioned such that it extends through the knockout opening in the junction box and terminates within the junction box. In one application, the end extending into the junction box is threaded for receipt of a securing nut which is installed from the inside of the junction box, thus mechanically securing the connector to the box. In another application, examples of which are disclosed in U.S. Pat. Nos. 3,174,776 and 3,556,566, the cylindrical body of the connector is formed in a split-shell arrangement, whereupon tightening of the screw against the conduit causes the respective shells of the connector body to expand outwards thereby engaging the walls of the junction box about the opening.
Although the split-shell connector eliminates the need for a separate securing nut (which is often difficult to install due to limited room in the junction box), split-shell connectors are more susceptible to failure resulting from application of a moment to the connector. For example, a bending force experienced by the connector (which may be imparted thereon by rigid conduit such as EMT) may cause relative axial movement between the upper end lower body portion of the connector which, in turn, may be sufficient to allow pullout of the conduit from the connector or pullout of the connector from the junction box. The split-shell connectors are particularly susceptible to this type of failure when EMT is employed as the electrical conduit. As a result, EMT has typically in the past been terminated at the junction box with a conventional connector and locknut.
Thus, there is a need in the art for a split-shell type connector having increased mechanical integrity thus providing increased resistance to pullout failure resulting from application of bending forces to the connector.